PLC Technobable.

This is an old post of ours in the blog we previously contributed to.


Audience Adept Response AR6P.


The topic of PLCs has been hot lately, hence I feel it's a subject worth investigating further. With this post, I will attempt to demystify some of the technical aspect of PLCs. In hope that a more informed buyer is a smarter buyer.

There are basically four types of PLCs competing in the market today. They are:

1) Passive Filters - These are the earliest and technically the most basic of methods. It merely involves filter caps of various values, coupled with cryogenitically treated contacts and sometimes add choke filter in to the power line. The sound characteristics of this type of PLC is rather un intrusive, especially when the design uses low value filter caps of 0.1uf like the Shunyata Hydra. It basically retains the sound of the system powered by it, but with further refinements at the top end and perhaps add a little bloom to the mids. Sometimes, in circuits where a power factor cap of 4.7uf is installed in the schematics, the bass will probably also tightened up a bit. Some models like the Shunyata Hydra 8 and Audio Magic Stealth XXX has compound screening to further reduce the effects of airborne RFI and EMI interference. The most successful representation of this type are Shunyata Hydras, Audio Magic Stealth series and Audience Adept Response models.





Audio Magic Stealth XXX.


Shunyata Hydra 4 undressed. Note the red MOV, grey circuit breaker, black 0.1uf filter X-2 caps and the cyro ed bus bars connecting the duplex receptacles.

Shunyata Hydra 6.

2) Transformer Based - It's really baffling what the good ol' transformer, with it's various winding schemes can produce so many varieties of PLCs. You have parallel choke based types like the RGPC 400P, and there's also the balance transformer type like those made locally by Promithues Audio. Also available are the booster transformers employed by Isotek Titan and finally, we have isolation transformers like the famed Torus Power and RGPC Substation. AVRs can also be transformer based, just like the Soundstage brand sold by Tong Lee. As for the sound of the transformer based PLC is harder to tell, as each version will have their own characteristics. For example, a balance transformer winding splits the 240V input voltage to two 120V lines. Both are wind along side each other to cancel out noise, just like our balance XLR interconnects. Booster transformer can reproduce more ampere at output than what was feeding it at the input, hence it'll always sound muscular and in control. Isolation transformers isolate your audio system plugged thru it from the rest of your house, allowing your system to be heard at it's full glory.

Torus Power RM8A undressed, note the huge isolation transformer.


RGPC Substation, isolation transformer inside too! Claims to supply peak 4000W, double the Torus Power RM8A s, 2000W.

3) Re generators - Here, we have the most technically challenging, and in theory should be the most correct way of treating power line noises. It's like having the power station supplying direct power to your audio system. It takes power from the wall, converts them to DC voltage, either stored in batteries or huge storage capacitors, then amplify the DC back in to AC voltage just like a power amp would. With the new class D designs, you can get very high efficiency, hence very high out put from a very manageable package, it runs cool too! The sound aspect is very predictable too, to a certain degree. Both the PS Audio Power Plant Premier and Pure Power models have that characteristic balls out bass control, eerily quiet back grounds, wide band width transient response and out of this world micro and macro dynamics. It really totally takes over and changes the sound of your system substantially.

Pure Power AC re generator, UPS and offers full feature protection for your hifi!


PS Audio Power Plant Premier AC re generator.

4) Hybrids - Labeled as such, it means that the PLC uses more than one of the above three methods to treat power line noises. Isotek is one such example, like in my Sigmas model, you can actually find booster transformers, passive filter and power factor caps, married to choke filters to isolate each output.


Isotek Sigmas, a true hybrid for great performance.

Despite all the PLC technobable, I don't think it's any more help full at all, as PLC performance in any case, are hard to gauge for the following reasons.

a) They are reactive to the power quality of the area. Hence different areas will require different solutions to the problem. And if the power quality of an area is good to start with, you'll probably not hear much of improvements with the PLC, but if the power quality is poor to start with, the sound improvement perceived will certainly be more.

b) Different system places different demands on PLCs. Like ampere hungry tube power amps and mega watt class A rated solid state amps are the hardest to drive and will place very unreasonable loads upon PLCs. Smaller systems can in fact be more sensitive to changes with a PLC added.

c) Every audiophile, depending on his/her hifi journey have different expectations on PLC performance.

d) Setting up of PLCs, some will invariably respond better to tweaks, like isolation than others. Even the quality of input power cables and contact plugs matter too.

Technical merits aside, the final advise is still to try before you buy! No other way to guarantee you get the most suitable PLC for your system and budget requirements.

Posted by Panzer 27 March '09